In an optical communication system, chromatic dispersion generated in an optical fiber, which is a component of an optical transmission path, induces waveform distortions in optical signals. In order to assure a satisfactory signal quality, chromatic dispersion accumulated while an optical signal is transmitted through the optical transmission path is compensated for on the receiving side.
Further, as the transmission distance of optical signals is increased, the influence of the wavelength dependency of chromatic dispersion (dispersion slope) cannot be ignored. In other words, in order to suppress waveform distortions, the values of chromatic dispersion to be compensated for in channels on a shorter wavelength side is different from those in channels on a longer wavelength side.
An example optical transmission path may be configured from a transmission fiber, such as a non zero-dispersion shifted fiber (NZ-DSF), and a dispersion compensating fiber (DCF). In this configuration, with the wavelength dependency of the chromatic dispersion (dispersion slope) of 0.1 ps/nm/km/nm, the transmission path length of the optical transmission path of 10000 km, and the light wavelength in a range from 1545 nm to 1555 nm, the chromatic dispersion in the optical transmission path deviates in a range of 10000×0.1×10=10000 ps/nm.
In other words, even when the dispersion at a light wavelength of 1550 nm is as small as +0 ps/nm/km, chromatic dispersion deviates in a range of 10000 ps/nm for light ranging from 1545 nm to 1555 nm.
The following Patent Reference 1 discloses a dispersion compensation device.    Patent Reference 1: WO 2001/006682